It is known to produce an entwined yarn from a bundle of spinning fibers emerging from a pair of delivery rollers of a drafting device and a binding thread running off a bobbin which are taken together through a rotating hollow spindle (DT-OS 1,685,881, DT-OS 2,428,483, US-PS 3,831,369, DT-OS 2,407,357). In the course of this operation, the binding thread wraps helically round the bundle of spinning fibers producing a yarn with the strength necessary for its further processing, which is then drawn out of the hollow spindle by a pair of draw-off rollers and wound on a bobbin.
Thus a yarn can be produced in a particularly economical manner with a high production speed, but difficulties arise if piecing has to be effected, for example after a thread breakage. The operator is then faced with the task of connecting together three components, namely the bundle of spinning fiber, the binding thread and the free end of the already finished entwined yarn.
It has already been proposed, for piecing an entwined yarn, to use a compressed-air pistol with a suction tube, by means of which a reduced pressure is produced in the tube or the hollow spindle lying in the center of the binding-thread bobbin so that the bundle of spinning fibers or sliver and the binding thread withdrawn from the rotating bobbin are sucked through the hollow spindle DT-OS 2,428,483). In the course of this, the sliver is strengthened to such an extent that the yarn emerging from the hollow spindle can be taken through the pair of draw-off rollers and laid on the bobbin. A disadvantage of this piecing method is that only two components are united to one another and no connection is effected between the end of the already finished entwined yarn and the end of the yarn emerging from the hollow spindle so that there is a yarn breakage on further processing. Furthermore, the case may arise that the speed of the suction air in the pistol is so high that the bundle of spinning fibers is not bound by the rotating binding thread or that the reduced pressure is too low so that the binding thread is not pulled off the bobbin.